Influence of neutron activation factors on matrix tablets for site specific delivery to the colon

The impact of the neutron activation procedure, i.e. incorporation of samar ium oxide (Sm2O3) and neutron irradiation, on the compression properties (i ncluding the crushing strength) and in vitro dissolution of potential colon ic delivery systems based on matrix tablets of amidated pectin (Am.P) or tw o types of hydroxypropyl methylcellulose (HPMC) was investigated. The neutr on activation factors did not influence the compression properties of the t ablets. Replacement of magnesium stearate with samarium stearate in directl y compressed Am.P tablets to achieve both radiolabelling and lubrication re sulted in a greater extent of concentration-dependent reduction of the crus hing strength. Dissolution tests demonstrated that irradiation increased th e release of the model drug ropivacaine from the tablets. The extent of thi s increase was unexpectedly low considering the previously observed degrada tion of the polymer expressed as an irradiation-induced viscosity reduction in solutions prepared from the polymers. Delayed-release coating with Eudr agit(R) L 100 protected the HPMC tablets against the release-increasing eff ect of irradiation until the late phases of release. Sm2O3 retarded the rel ease to a varying extent depending on particle characteristics. Incorporati on of Sm2O3 in the coating layer did not influence the release. However, on e-third of the radioactivity leached from the coating within 60 min in 0.1 M HCl. (C) 2000 Elsevier Science B.V. All rights reserved.